My plan would be 1/8 bspt to 4an adapter in the block and take the 4an up to the firewall to the tee/cross there. I'd rather not have 3 or 4 oil connections underneath the intake manifold. I couldn't find a 4an x 1/8 bspt x 4an tee last time I looked online but I'll recheck.

There's so many 1/8bsp plugs on a Miata head it's really easy to grab oil from one of them.